A surge event in a gas turbine engine may occur when pressure at the delivery end of a gas turbine compressor becomes high as a result, for example, of reduced flow at the compressor outlet. In such circumstances, compressor pressure at the delivery end of the gas turbine engine may increase as air flow decreases. This may cause an air flow reversal. Such flow reversal may release the sudden pressure that has developed on account of reduced flow. The flow reversal may be accompanied by a loud noise and/or tremendous vibration. A surge event may affect the whole engine and, if it is of high enough magnitude, the gas turbine can be damaged or destroyed.
Anti-surge devices are sometimes installed on gas turbine engines to allow air flow to be reduced even on low speeds and to keep a certain air flow from the compressor during times of low air requirement (e.g. startup and shutdown). Some prior art systems have prevented compressor surges in turbine engines by using a pneumatic device which bleeds air when pressure at or before the compressor inlet surpasses a reference pressure, normally employing a single choice of bleed size. Improvement in compressor surge prevention in gas turbine engines is desirable.